Communication Apparatus, Transmitting Method and Receiving Method

ABSTRACT

A communication apparatus that performs receiving processing of data transmitted at timings of a predetermined interval, the communication apparatus having a transmitting unit configured to transmit a signal indicating that a data is successfully received when the data transmitted at M th  timing according to the predetermined interval is successfully received and a control unit configured to perform a control for providing a period in which other receiving processing different from the receiving processing is at least performed or a receiving process is not performed until when next M+1 th  timing comes according to the predetermined interval after the transmission of the signal.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority ofprior Japanese Patent Application No. 2007-208765, filed on Aug. 10,2007, the entire contents of which are incorporated herein by reference.

BACKGROUND

1. Field

An aspect of the invention is related to communication apparatusesincluding a transmitting apparatus and a receiving apparatus, atransmitting method, and a receiving method for transmitting/receivingwireless signals.

2. Description of the Related Art

In wireless communication systems including a mobile communicationsystem, wireless signals are transmitted to a receiving apparatus from atransmitting apparatus. Packet data or the like is an example of thewireless signals. There are various data which is stored in a data partof the packet data. The data is not limited to text data and image data,but may include audio data or the like. If the wireless signals are nottransmitted continuously, the transmission of the wireless signal isgenerally performed at a predetermined interval. For example, thetransmission is performed every 20 ms.

However, there is no guarantee that the receiving apparatus cansuccessfully receive the wireless signal even though the transmittingapparatus transmits the wireless signal. That is, a transmit signal isinfluenced by a propagation channel (path) (e.g., a fading channel)because the transmission and reception are performed wirelessly.Accordingly, a receive signal that the receiving apparatus obtains byreceiving the transmit signal may not be correct. The transmit signalcan be error-correcting coded, and it is possible to generate anappropriate receive signal by error-correct encoding in the receivingapparatus. However, the error may not be corrected completely dependingon the extent of the error, so that the receiving apparatus may notobtain the appropriate receive signal.

In consideration of the above described matter, there is a technologyfor performing a retransmission from the transmitting apparatus bydetermining reception result of the transmit signal in the receivingapparatus and feeding back the reception result to the transmittingapparatus.

FIG. 1 shows a known method of data transmitting/receiving processing inwhich the retransmission control is introduced.

As described in FIG. 1, the transmitting apparatus transmits the data(e.g., audio packet data) in turns every 20 ms. The receiving apparatusattempts to receive the transmitted data. Then the receiving apparatustransmits an ACK signal when the data is successfully received. Thetransmitting apparatus recognizes that the transmission was performedsuccessfully if the ACK signal is received and then transmits othertransmit signal (e.g., a next transmit signal which is to be transmittedto the same receiving apparatus) at next transmit timing. However, asdescribed in FIG. 1, when the receiving apparatus could not receive thedata successfully since a third transmission became an error because ofthe influence of the wireless channel, the receiving apparatus transmitsa NACK signal. The transmitting apparatus recognizes that thetransmission was not performed successfully if the NACK signal isreceived and then performs the retransmission. Thus, the receivingapparatus further receives the retransmitted data. When the reception ofthe retransmission is successful, an ACK signal is transmitted from thereceiving apparatus and then next data is transmitted from thetransmitting apparatus at the next transmit timing. Accordingly, even ifa first transmission fails, it is possible that one or more than oneretransmission makes the transmission a success by introducing theretransmission control.

As for the above described retransmission control are described in 3GPPTS25.212, 3GPP TS25.321 and 3GPP TS36.212.

As described previously, introducing the retransmission controlincreases chances of successful data transmission from the transmittingapparatus to the receiving apparatus. However, it is difficult toperform a control such as to perform an intermittent reception simply ata predetermined interval, because the retransmission control isperformed (inserted).

SUMMARY

It is an object of the present invention to reduce waste in a receptionoperation and/or a transmission operation when retransmissions occur outof the predetermined interval because of the retransmission control.

According to an aspect of the invention, a communication apparatus thatperforms receiving processing of data transmitted at timings of apredetermined interval, the communication apparatus having atransmitting unit configured to transmit a signal indicating that a datais successfully received when the data transmitted at M^(th) timingaccording to the predetermined interval is successfully received and acontrol unit configured to perform a control for providing a period inwhich other receiving processing different from the receiving processingis at least performed or a receiving process is not performed until whennext M+1^(th) timing comes according to the predetermined interval afterthe transmission of the signal or method used in the communicationapparatus is utilized.

According to an aspect of the invention, a communication apparatus thatperforms receiving processing of data transmitted at timings of apredetermined interval, the communication apparatus having atransmitting unit configured to transmit a signal indicating that a datais not successfully received when the data is not successfully receivedat M^(th) timing according to a predetermined interval and a controlunit configured to perform a control for providing a period in whichother receiving processing different from the receiving processing is atleast performed or a receiving process is not performed until when nextM+1^(th) timing comes according to the predetermined interval after itis detected that retransmission control processing is not performed inresponse to the transmission of the signal indicating that the data isnot successfully received or method used in the communication apparatusis utilized.

According to an aspect of the invention, a communication apparatuscapable of performing a retransmission, the communication apparatushaving a retransmission control unit configured to perform aretransmission when a response to new data is not received is receivedand when a signal indicating that the data is not successfully receivedis received, wherein the retransmission control unit does not perform anN^(th) retransmission when a response to the N^(th) retransmission isnot received, but performs an N+1^(th) retransmission when a responseindicating that the N^(th) retransmission is not successfully receivedis received or method used in the communication apparatus is utilized.

According to an aspect of the invention, a communication apparatus thatperforms receiving processing of data transmitted at timings of apredetermined interval, the communication apparatus having atransmitting unit configured to transmit a signal indicating that a datais successfully received when the data transmitted at M^(th) timingaccording to the predetermined interval is successfully received and acontrol unit configured to determine whether or not a retransmissioncontrol processing is performed when the signal indicating that the datais successfully received is transmitted, wherein the control unittransmits a signal indicating that the data is successfully receivedwhen the retransmission control processing is performed or method usedin the communication apparatus is utilized.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or maybe learned by practice of the invention. Theobjects and advantages of the invention will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a known method of data transmitting/receivingprocessing.

FIG. 2 illustrates a first example of transmitting/receiving processing.

FIG. 3 illustrates a second example of transmitting/receivingprocessing.

FIG. 4 illustrates a first example of a configuration of a receivingapparatus.

FIG. 5 illustrates an example of a control flow in the receivingapparatus.

FIG. 6 illustrates another example of a control flow in the receivingapparatus.

FIG. 7 illustrates a retransmission control of a case when atransmitting apparatus does not receive an ACK signal.

FIG. 8 illustrates a first example of a configuration of a transmittingapparatus.

FIG. 9 illustrates a first example of transmitting processing.

FIG. 10 illustrates an example of a control flow in the transmittingapparatus.

FIG. 11 illustrates a second example of transmitting processing.

FIG. 12 illustrates an example of a control flow in the receivingapparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be explained withreference to accompanying drawings.

[a] First Embodiment

When a transmitting apparatus transmits a wireless signal at apredetermined interval, a receiving apparatus can receive the wirelesssignal by performing a reception in response to the predeterminedinterval. It is possible to determine whether or not a transmission (aretransmission) is performed out of the interval based on the type ofsignal the receiving apparatus itself transmits. That is, thetransmission (the retransmission) does not occur out of the interval ifan ACK signal (type 1) is transmitted from the receiving apparatus, butthe transmission (the retransmission) occurs out of the interval if aNACK signal (type 2) is transmitted from the receiving apparatus.

In this embodiment, therefore, when the receiving apparatus performingan intermittent reception control in response to a transmission intervaltransmits the NACK signal, the reception operation period has to be setto be longer comparing to the case when the ACK is transmitted. Theperiod can be, for example, a period in which the wireless signal istransmitted by a retransmission (e.g., a first retransmission) and thenreceived. If another NACK signal is transmitted in response to theretransmission, the period can be a period in which the wireless signalis transmitted by another retransmission (a second retransmission) andthen received.

At the time of transmitting NACK signals, the power of a receiving unitis turned on all through the period corresponding to the transmissioninterval. At the time of transmitting ACK signals, the power of thereceiving unit can be turned off when the reception is completed, whichcan reduce power consumption.

However, in a situation where it is assumed that a reception environmentis not so good, such as the environment in which NACK signals aretransmitted, the receiving unit may allocate equal to or more than ½ to⅔ of the transmission interval to the period for receiving theretransmission and allocates the remaining ⅓ to ½ of the transmissioninterval to the period for measuring (search) a reception quality ofsignals from adjacent base stations. That is, a receiving processingunit can be controlled to perform other receiving processing.

FIG. 2 shows a first example of transmitting/receiving processing.

As described in FIG. 2, the transmitting apparatus transmits the data(e.g., audio packet data), for example, every 20 ms. The receivingapparatus performs the intermittent reception in response to thisinterval. When the data is successfully received and an ACK signal istransmitted, a predetermined period (T1) is allocated to the receptionoperation of receiving the data. When a NACK signal is transmitted,another predetermined period (T2(T1<T2)) is allocated to the receptionoperation of receiving the data. The period T2 is a period in which atleast one retransmission can be received. When a plurality of theretransmissions are performed, the period T2 can be set to a period TLin which a final retransmission can be received.

A second example is that the transmitting apparatus may not receive theNACK signal even though the receiving apparatus transmits the NACKsignal. In such case, the retransmission is not performed. Thus, anotherNACK signal can be transmitted to expect another retransmission, butthis requires a considerable time.

Therefore, when the retransmission is not successfully received eventhough the receiving apparatus transmits the NACK signal (or when thetransmitting apparatus does not receive an advance notice ofretransmission), the receiving apparatus can control the receiving unitnot to perform the reception operation of receiving the data until thenext periodic transmit timing comes. That is, for example, the power ofthe receiving unit can be turned off or the receiving unit can searchfor another transmitting unit as an out of the reception standby mode.

FIG. 3 shows a second example of the transmitting/receiving processing.

As described in FIG. 3, when the receiving apparatus could not receivethe first transmit signal, the receiving apparatus transmitted a NACKsignal to attempt to receive the retransmission, but did not receive theretransmission (or did not receive an advance notice of retransmission).Thus, the receiving apparatus then puts the receiving unit out of areception standby state of retransmit data. On the other hand, thereceiving apparatus transmits the NACK signal to the transmittingapparatus because a third transmit signal was not received successfully.In this case, the retransmission is performed because the transmittingapparatus could receive the NACK signal. The receiving apparatustransmits an ACK signal because the receiving apparatus could receivethe first retransmission, and puts the receiving unit out of thereception standby state of the retransmit data. The operation out of thereception standby state can be identical to that of the first example.

Basic control flows of the first and second examples according to thefirst embodiment are described above. A configuration of the receivingapparatus corresponding to the above described control will be describedby using FIG. 4.

FIG. 4 shows a first example of a configuration of the receivingapparatus.

Numeral 1 indicates a receiving antenna. Numeral 2 indicates a receivingprocessing unit. Numeral 3 indicates a reception result determiningunit. Numeral 4 indicates a reception control unit. Numeral 5 indicatesa timer. Numeral 6 indicates an ACK/NACK signal generating unit. Numeral7 indicates a transmitting processing unit. Numeral 8 indicates atransmitting antenna.

The receiving antenna 1 receives transmit signals transmittedperiodically from the transmitting apparatus and transmit signalsretransmitted from the transmitting apparatus. The receiving processingis performed on the signals which are received by the receiving antennaby the receiving processing unit 2 depending on transmission forms usedfor the transmission in order to obtain receive data by demodulating anddecoding (error correcting decoding may be included). The transmissionform can be included in the advance notice of transmission transmittedfrom the transmitting apparatus or can be presumed to be a form selectedfrom predetermined forms. The receive data obtained by the receivingprocessing unit 2 is given to the reception result determining unit 3.Then it is determined whether or not the reception is performedsuccessfully. For example, if the transmitting apparatus performserror-detection encoding processing (adding a CRC calculation result orthe like) on the transmit data, an error detection is performed by usingCRC calculation result and the error-detection result is given to theACK/NACK signal generating unit 6. If the data is successfully received,the receive data is given to a received data processing unit on the leftside which is not shown in the figure and then is displayed on adisplay, outputted as audio sound from a speaker, or outputted to anexternal unit as needed. Although the data can be discarded if the datais not successfully received, the data can be stored in a memory unitinside the reception result determining unit 3 in order to be combinedwith the receive data transmitted by a next retransmission. Thereceiving processing unit 2 can perform the decoding based on thecombined data and can give the result to the reception resultdetermining unit 3 (a so-called hybrid ARQ method).

If the reception result indicates that the data was successfullyreceived, the ACK/NACK signal generating unit 6 outputs an ACK signal asa response signal. If the reception result indicates that the data wasnot successfully received, the ACK/NACK signal generating unit 6 outputsa NACK signal as a response signal. The transmitting processing unit 7performs transmitting processing on the response signals (the ACKsignal/the NACK signal) to convert it into wireless signals and thentransmits the wireless signals from the transmitting antenna 8. Thetransmit timing of the response signal can come after a predeterminedoffset time passes the transmit timing of the packet.

The transmitting antenna and the receiving antenna can be a sharedantenna by using a duplexer or the like.

The reception control unit 4 controls each receiving unit based ontiming signals outputted from the timer 5 (timing managing unit). Otherunits are controlled by a control unit 9.

FIG. 5 shows a first example of a control flow within the receivingapparatus. This control is performed mainly by a control of thereception control unit 4.

The reception control unit 4 controls to start the reception operationand determines whether or not the packet is received (step S1).

If the packet is received in step S1, the reception result determiningunit 3 determines whether or not the packet is successfully received(step S2).

If the packet is successfully received, an ACK signal is generated bythe ACK/NACK signal generating unit 6 and the ACK signal is transmittedfrom the transmitting processing unit 7 and the transmitting antenna 8(step S3).

If the packet is not successfully received, on the other hand, a NACKsignal is generated by the ACK/NACK signal generating unit 6 and theNACK signal is transmitted from the transmitting processing unit 7 andthe transmitting antenna 8 (step S5). The reception control unit 4 putsthe receiving processing unit 2 etc. in the reception standby statewithout turning off the power thereof, or the like, in order to receivea retransmit packet. After that, the process goes back to thedetermination of step S1.

If the ACK signal is received in step S3, receiving stop processing ofthe packet data is performed (step S4). As the receiving stop processingof the packet data, for example, the power of the receiving processingunit 2 or the like is turned off or the search of the other transmittingapparatuses may be conducted.

Then the reception control unit 4 controls the receiving processing unit2 etc. at the next transmit timing to receive a next packet. The processgoes back to the determination of step S1.

If it is determined that the packet is not received at the predeterminedperiodic transmit timing in the determination of step S1, it isdetermined whether or not the retransmit packet is received in step 1without turning off the power of the receiving processing unit 2 justlike the process after transmitting the NACK signal in step 5 (Step S1).

FIG. 6 shows another example of a control flow within the receivingapparatus. This control is performed by the control of the receptioncontrol unit 4 or the like.

The reception control unit 4 controls to start the reception operationin response at the transmit timing and determines whether or not thepacket is received (step S11).

If the packet is received in step S11, the reception result determiningunit 3 determines whether or not the receive packet is receivedsuccessfully (step S12).

If the packet is successfully received, an ACK signal is generated bythe ACK/NACK signal generating unit 6 and is transmitted from thetransmitting processing unit 7 and the transmitting antenna 8 (stepS13).

If the packet is not successfully received, on the other hand, a NACKsignal is generated by the ACK/NACK signal generating unit 6 and istransmitted from the transmitting processing unit 7 and the transmittingantenna 8 (step S15). The reception control unit 4 puts the receivingprocessing unit 2 etc. in the reception standby state without turningoff the power thereof, or the like, in order to receive the retransmitpacket. After that, the process goes back to the determination in stepS11.

If the packet is not received in step S11 or the ACK signal is receivedin step S13, the receiving processing of the packet data is stopped(step S14). As the stop of the receiving processing of the packet data,for example, the power of the receiving processing unit 2 or the like isturned off or the search of the other transmitting apparatuses isconducted.

Then the reception control unit 4 controls the receiving processing unit2 and the like at the next transmit timing to receive the next packet.The process goes to the determination of step S11.

[b] Second Embodiment

The transmitting apparatus can perform a retransmission control not onlywhen the ACK signal is not received but also when the NACK signal isreceived.

FIG. 7 shows the retransmission control when the transmitting apparatusdoes not receive the ACK signal.

As well as in the first embodiment, the transmitting apparatus transmitspackets at the predetermined interval (20 ms). The first transmissionwas successful and the receiving apparatus transmitted an ACK signal.However, the transmitting apparatus could not receive the ACK signalsuccessfully (or the transmitting apparatus incorrectly determined theACK signal as a NACK signal). Accordingly, the transmitting apparatusperforms a retransmission.

On the other hand, since the receiving apparatus transmitted the ACKsignal, the retransmission is not expected and the receiving apparatusdoes not receive the retransmission. Therefore, the transmittingapparatus performs another retransmission because the receivingapparatus does not transmit any response signals (an ACK signal/a NACKsignal) in response to the retransmission. After that, uselessretransmissions are performed up to the maximum transmission number invain until when the next transmit timing comes.

In this embodiment, the transmitting apparatus does not perform the nextretransmission if the NACK signal is not received in response to thefirst retransmission. That is, the retransmission is performed not onlywhen the NACK signal is received but also when the ACK signal is notreceived in response to the first retransmission. After the firstretransmission, however, the retransmission is performed if the NACKsignal is received, but the retransmission is not performed if theACK/NACK signal is not received (no response case).

As a result, it is possible to reduce the useless retransmissions whichare performed when the transmitting apparatus can not detect the ACKsignal.

FIG. 8 shows a first example of a configuration of the transmittingapparatus.

Numeral 11 indicates a receiving antenna. Numeral 12 indicates areceiving processing unit. Numeral 13 indicates a retransmission controlunit. Numeral 14 indicates a packet generating unit. Numeral 15indicates a packet information generating unit. Numeral 16 indicates atransmitting processing unit. Numeral 17 indicates a transmittingantenna.

The receiving antenna 11 receives various signals (e.g., ACK signals andNACK signals) transmitted from the receiving apparatus. The receivingprocessing is performed on the signals received by the receiving antennaby the receiving processing unit 12 depending on the transmission formsused for the transmission in order to obtain the receive data bydemodulating and decoding (error correcting decoding may be included).The receiving data (e.g., an ACK signal and a NACK signal) obtained bythe receiving processing unit 12 is given to the retransmission controlunit 13.

After the new transmission (non-retransmission) (the transmissionperformed at the predetermined interval), the retransmission controlunit 13 performs the retransmission control when neither ACK nor NACKsignal is received at the timing of receiving the response signal (theACK signal/the NACK signal).

That is, retransmit data is generated based on the transmit data storedin the packet generating unit 14 and is transmitted from thetransmitting processing unit 16 and the transmitting antenna 17.

In this example, the information about the packet form transmitted fromthe packet generating unit 14 is given to the packet informationgenerating unit 15. Then a transmission parameter (information such as apacket size, an encoding method, a modulating method, and a MIMO(applied/not applied)) is generated by the packet information generatingunit 15. In advance of the packet transmission, the transmissionparameter is transmitted as advance information (including a notice oftransmission performed to a certain receiving apparatus) from thetransmitting processing unit 16 and the transmitting antenna 17.

When the modulating method is changed by changing the transmissionparameter, the modulating method is informed to the transmittingprocessing unit 16, and the transmitting processing unit 16 transmitsthe packet in accordance with the informed modulating method.

The transmitting antenna and the receiving antenna can be a sharedantenna by using a duplexer or the like.

In this case, the retransmission control unit 13 performs theretransmission in response to the first transmission (the newtransmission) when the ACK signal is not received (including the casewhen the NACK signal is received). However, after N^(th) transmission(including the N^(th) transmission), the retransmission control unit 13does not perform the retransmission unless the NACK signal is received.In this case, the number N can be a predetermined value which is 2 orgreater. However, the number N can be less than the maximumretransmission number (such as the maximum retransmission number−1).

FIG. 9 shows a first example of this transmitting/receiving processing.

As shown in FIG. 9, the retransmission control unit 13 performs theretransmission control when the transmitting apparatus could not detectthe ACK signal (at the predetermined timing of receiving responsesignals) or detect the NACK signal incorrectly even though the first(the new) transmission of the packet data was successful and thereceiving apparatus transmitted the ACK signal.

However, since the receiving apparatus transmitted the ACK signal, thereceiving apparatus does not perform the reception operation of theretransmit packet (turns off the power of the receiving processing unitor search other transmitting apparatus) and does not transmit theresponse signal either.

Therefore, the transmitting apparatus does not receive the ACK signal orthe NACK signal at the timing of receiving the response signal inresponse to the retransmission. Then, if the transmitting apparatus doesnot receive the NACK signal, the retransmission control unit 13 of thetransmitting apparatus controls the transmitting apparatus not toperform the retransmission.

FIG. 10 shows a first example of a control flow in the transmittingapparatus. This control is performed mainly by the control of theretransmission control unit 13.

The transmitting apparatus (the retransmission control unit 13)determines whether or not there is a transmit packet which should betransmitted (step S31).

If NO in step S31, the process goes back to step S31. If YES in stepS31, the packet generating unit 14 gives the transmit packet to thetransmitting processing unit 16 in order to transmit a new packet (stepS32) and transmits the packet from the transmitting antenna 17. Inadvance of the packet transmission, transmission parameter informationis generated by the packet information generating unit 15 and is alsotransmitted to the receiving apparatus from the transmitting processingunit 16 and the transmitting antenna 17.

Then the retransmission control unit 13 sets a value i of a transmissioncounter to 0 (Step S33). The counter may be provided in theretransmission control unit 13.

Next, the retransmission control unit 13 determines whether or not theresponse signal is received. If the ACK signal is received, the processgoes back to step S31. Then it is determined whether or not there is thenext transmit packet.

On the other hand, if the NACK signal is received as the responsesignal, the retransmission control unit 13 controls the transmittingapparatus to retransmit the packet (step S35) and increments the value iof the counter by only one. Then the process goes back to thedetermination of step S34.

In the determination of step S34, it is determined that DTX (noresponse) is indicated if no ACK signal or no NACK signal is detected asthe response signal. Then it is determined whether or not the value i ofthe counter is greater than a predetermined value k (step S36). Thevalue k is a counting number which is 2 or greater than 2 and may beless than the maximum retransmission number.

In step S36, if the setting value of the counter is greater than thevalue k, the retransmission control unit 13 does not performretransmitting processing. The process goes back to step S31 and theretransmission control unit 13 transmits the next new packet.

On the other hand, if the setting value of the counter is less than thevalue k in step S36, the retransmission control unit 13 transmits theretransmit packet (step S35) and increments the value i of the counterby only one. Then the process goes back to step S34.

This makes it possible to reduce the useless retransmissions even ifthere is a recognition difference of the reception result between thetransmitting apparatus and the receiving apparatus.

Next, FIG. 11 shows a second example of this transmitting/receivingprocessing.

As described in FIG. 11, the retransmission control unit 13 performs theretransmission control when the transmitting apparatus could not detectthe ACK signal (at the timing of receiving the predetermined responsesignal) or detect the NACK signal incorrectly even though the first (thenew) transmission of the packet data was successful and the receivingapparatus transmitted the ACK signal.

An accidental case is considered in which that the transmittingapparatus can not detect the ACK signal even though the receivingapparatus transmits the ACK signal. Thus, it is determined whether ornot the retransmit packet is transmitted. At this time, thedetermination can be performed by checking for an advance notice ofretransmission transmitted from the packet information generating unit15 or by actually attempting to receive the retransmitted packet.

If it is detected that the retransmission is not performed, thereceiving apparatus turns off the power of the receiving unit or thesearch of other transmitting apparatuses is performed.

On the other hand, if it is detected that the retransmission isperformed even though the transmitting apparatus transmitted the ACKsignal, the receiving apparatus transmits the ACK signal regardless ofwhether or not the retransmit packet was received successfully. This isbecause since a successful reception has already been completed withrespect to the packet, another retransmission is not necessary.

Therefore, because this ACK signal is received by the transmittingapparatus, the retransmission control unit 13 of the transmittingapparatus is controlled not to perform another retransmission.

FIG. 12 shows a first example of a control flow within the receivingapparatus. This control is performed mainly by the control of thereception control unit 4. That is, the receiving apparatus having theconfiguration shown in FIG. 4 is applicable.

The transmitting/receiving apparatus (the reception control unit 4)controls to start the reception operation at the transmit timing fortransmitting a new packet in response to the predetermined interval anddetermines whether or not the packet is received (step S41).

If the packet is received in step S41, the reception result determiningunit 3 determines whether or not the packet is successfully received(step S42).

If the packet is successfully received, an ACK signal is generated bythe ACK/NACK signal generating unit 6 and the ACK signal is transmittedfrom the transmitting processing unit 7 and the transmitting antenna 8(step S43).

If the packet is not successfully received, on the other hand, a NACKsignal is generated by ACK/NACK signal generating unit 6 and the NACKsignal is transmitted from the transmitting processing unit 7 and thetransmitting antenna 8 (step S46). The reception control unit 4 puts thereceiving processing unit 2 etc. in the reception standby state withoutturning off the power thereof, or the like, in order to receive theretransmit packet. After that, the process goes back to thedetermination of step S41.

If an ACK signal is transmitted in step S43, the reception control unit4 determines whether or not the retransmit packet is received (stepS44). In this step, if the transmitting processing of the retransmitpacket is not performed (if the advance notice of transmission is notreceived or if the transmit packet is not actually received), thereceiving processing of the packet data is stopped (step S45). As thestop of the receiving processing of the packet data, for example, thepower of the receiving processing unit 2 or the like is turned off orthe search of other transmitting apparatuses is performed.

Then the reception control unit 4 controls the receiving processing unit2 or the like at the next transmit timing to receive the next packet.Then the process goes back to the determination of step S41.

In step S44, if it is detected that the transmitting processing of thetransmit packet is performed even though an ACK signal is transmitted,the process goes back to step S43. Then the ACK signal is transmitted inorder to control the transmitting apparatus not to perform anotherretransmission.

Going back to step S43 from step S44 can be limited to only one time.Also, it is allowed to follow the route to go back to step S43 from stepS44 until the predetermined value N is reached. In this case, thepredetermined value N may be less than the maximum retransmissionnumber−1.

According to the embodiments, it is possible to reduce waste in thereception operation and the transmission operation when retransmissionsoccur out of the predetermined interval because of the retransmissioncontrol.

Although the embodiments of the present invention has been described indetail, it should be understood that the various changes, substitutions,and alterations could be made hereto without departing from the spiritand scope of the invention.

1. A communication apparatus that performs receiving processing of datatransmitted at timings of a predetermined interval, the communicationapparatus comprising: a transmitting unit configured to transmit asignal indicating that a data is successfully received when the datatransmitted at M^(th) timing according to the predetermined interval issuccessfully received; and a control unit configured to perform acontrol for providing a period in which other receiving processingdifferent from the receiving processing is at least performed or areceiving process is not performed until when next M+1^(th) timing comesaccording to the predetermined interval after the transmission of thesignal.
 2. The communication apparatus according to claim 1, wherein thetransmitting unit performs a reception control on a retransmission of adata transmitted at N^(th) timing until when next N+1^(th) timing comesaccording to the predetermined interval after transmitting the signalindicating that the data transmitted at the N^(th) timing is notsuccessfully received when the data transmitted at N^(th) timingaccording to the predetermined interval is not successfully received andperforms a control for providing a period in which other receivingprocessing different from the receiving processing is at least performedor a receiving process is not performed until when the next N+1^(th)timing comes according to the predetermined interval is performed.
 3. Acommunication apparatus that performs receiving processing of datatransmitted at timings of a predetermined interval, the communicationapparatus comprising: a transmitting unit configured to transmit asignal indicating that a data is not successfully received when the datais not successfully received at M^(th) timing according to apredetermined interval; and a control unit configured to perform acontrol for providing a period in which other receiving processingdifferent from the receiving processing is at least performed or areceiving process is not performed until when next M+1^(th) timing comesaccording to the predetermined interval after it is detected thatretransmission control processing is not performed in response to thetransmission of the signal indicating that the data is not successfullyreceived.
 4. A communication apparatus capable of performing aretransmission, the communication apparatus comprising: a retransmissioncontrol unit configured to perform a retransmission when a response tonew data is not received is received and when a signal indicating thatthe data is not successfully received is received, wherein theretransmission control unit does not perform an N^(th) retransmissionwhen a response to the N^(th) retransmission is not received, butperforms an N+1^(th) retransmission when a response indicating that theN^(th) retransmission is not successfully received is received.
 5. Acommunication apparatus that performs receiving processing of datatransmitted at timings of a predetermined interval, the communicationapparatus comprising: a transmitting unit configured to transmit asignal indicating that a data is successfully received when the datatransmitted at M^(th) timing according to the predetermined interval issuccessfully received; and a control unit configured to determinewhether or not a retransmission control processing is performed when thesignal indicating that the data is successfully received is transmitted,wherein the control unit transmits a signal indicating that the data issuccessfully received when the retransmission control processing isperformed.
 6. The communication apparatus according to claim 5, whereina determination is performed based on an advance notice ofretransmission of the data or an actual reception of the retransmission.7. A receiving method for performing receiving processing of datatransmitted at timings of a predetermined interval, the receiving methodcomprising: transmitting a signal indicating that a data is successfullyreceived when the data is successfully received at M^(th) timingaccording to the predetermined interval; and performing a control forproviding a period in which other receiving processing different fromthe receiving processing is at least performed or a receiving process isnot performed until when next M+1^(th) timing comes according to thepredetermined interval after the transmission of the signal.
 8. Areceiving method for performing receiving processing of data transmittedat timings of a predetermined interval, the receiving method comprising:transmitting a signal indicating that a data is not successfullyreceived when the data is not successfully received at M^(th) timingaccording to the predetermined interval; and performing a control forproviding a period in which other receiving processing different fromthe receiving processing is at least performed or a receiving process isnot performed until when next M+1^(th) timing comes according to thepredetermined interval after it is detected that retransmission controlprocessing is not performed in response to the transmission of thesignal indicating that the data is not successfully received.
 9. Atransmitting method of a communication apparatus capable of performing aretransmission, the method comprising: performing a retransmission whena response to new data is not received and when a signal indicating thatthe data is not successfully received is received, and not performing anN+1^(th) retransmission when a response to an N^(th) retransmission isnot received, but performs the N+1^(th) retransmission when a responseto the N^(th) retransmission is not successfully received is received.10. A receiving method of a communication apparatus that performsreceiving processing of data transmitted at timings of a predeterminedinterval, the receiving method comprising: transmitting a signalindicating that a data is successfully received when the datatransmitted at M^(th) timing according to the predetermined interval issuccessfully received; determining whether or not retransmission controlprocessing is performed when the signal indicating that the data issuccessfully received is transmitted; and transmitting a signalindicating that the data is successfully received when theretransmission control processing is determined to be performed.